The present invention relates to intake manifolds, for example, for use in motor vehicle gasoline engines equipped with an electronically controllable fuel injection system.
The term "aluminum" as used herein and in the appended claims includes pure aluminum, commercial aluminum containing a small amount of impurities and aluminum alloys. Further the term "wrought aluminum material" as used herein and in the appended claims includes products prepared by plastic working.
Intake manifolds have heretofore been prepared entirely by casting for use in motor vehicle gasoline engines equipped with an electronically controllable fuel injection system. However, since the cast product has a rough surface, the conventional intake manifold must be made smooth-surfaced at least in its interior by a cumbersome finishing procedure in order to assure diminished air resistance and thereby achieve an improved air intake efficiency. Further it is impossible to finish the entire interior surface of the intake manifold because of its configuration and therefore to fully reduce the air resistance for efficient air intake. Moreover, there is a limitation to the reduction of its weight.